xref: /freebsd/sys/dev/drm2/ttm/ttm_bo_api.h (revision a466cc55373fc3cf86837f09da729535b57e69a1)
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27 /*
28  * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
29  */
30 /* $FreeBSD$ */
31 
32 #ifndef _TTM_BO_API_H_
33 #define _TTM_BO_API_H_
34 
35 #include <dev/drm2/drmP.h>
36 
37 struct ttm_bo_device;
38 
39 struct drm_mm_node;
40 
41 
42 /**
43  * struct ttm_placement
44  *
45  * @fpfn:		first valid page frame number to put the object
46  * @lpfn:		last valid page frame number to put the object
47  * @num_placement:	number of preferred placements
48  * @placement:		preferred placements
49  * @num_busy_placement:	number of preferred placements when need to evict buffer
50  * @busy_placement:	preferred placements when need to evict buffer
51  *
52  * Structure indicating the placement you request for an object.
53  */
54 struct ttm_placement {
55 	unsigned	fpfn;
56 	unsigned	lpfn;
57 	unsigned	num_placement;
58 	const uint32_t	*placement;
59 	unsigned	num_busy_placement;
60 	const uint32_t	*busy_placement;
61 };
62 
63 /**
64  * struct ttm_bus_placement
65  *
66  * @addr:		mapped virtual address
67  * @base:		bus base address
68  * @is_iomem:		is this io memory ?
69  * @size:		size in byte
70  * @offset:		offset from the base address
71  * @io_reserved_vm:     The VM system has a refcount in @io_reserved_count
72  * @io_reserved_count:  Refcounting the numbers of callers to ttm_mem_io_reserve
73  *
74  * Structure indicating the bus placement of an object.
75  */
76 struct ttm_bus_placement {
77 	void		*addr;
78 	unsigned long	base;
79 	unsigned long	size;
80 	unsigned long	offset;
81 	bool		is_iomem;
82 	bool		io_reserved_vm;
83 	uint64_t        io_reserved_count;
84 };
85 
86 
87 /**
88  * struct ttm_mem_reg
89  *
90  * @mm_node: Memory manager node.
91  * @size: Requested size of memory region.
92  * @num_pages: Actual size of memory region in pages.
93  * @page_alignment: Page alignment.
94  * @placement: Placement flags.
95  * @bus: Placement on io bus accessible to the CPU
96  *
97  * Structure indicating the placement and space resources used by a
98  * buffer object.
99  */
100 
101 struct ttm_mem_reg {
102 	void *mm_node;
103 	unsigned long start;
104 	unsigned long size;
105 	unsigned long num_pages;
106 	uint32_t page_alignment;
107 	uint32_t mem_type;
108 	uint32_t placement;
109 	struct ttm_bus_placement bus;
110 };
111 
112 /**
113  * enum ttm_bo_type
114  *
115  * @ttm_bo_type_device:	These are 'normal' buffers that can
116  * be mmapped by user space. Each of these bos occupy a slot in the
117  * device address space, that can be used for normal vm operations.
118  *
119  * @ttm_bo_type_kernel: These buffers are like ttm_bo_type_device buffers,
120  * but they cannot be accessed from user-space. For kernel-only use.
121  *
122  * @ttm_bo_type_sg: Buffer made from dmabuf sg table shared with another
123  * driver.
124  */
125 
126 enum ttm_bo_type {
127 	ttm_bo_type_device,
128 	ttm_bo_type_kernel,
129 	ttm_bo_type_sg
130 };
131 
132 struct ttm_tt;
133 
134 /**
135  * struct ttm_buffer_object
136  *
137  * @bdev: Pointer to the buffer object device structure.
138  * @type: The bo type.
139  * @destroy: Destruction function. If NULL, kfree is used.
140  * @num_pages: Actual number of pages.
141  * @addr_space_offset: Address space offset.
142  * @acc_size: Accounted size for this object.
143  * @kref: Reference count of this buffer object. When this refcount reaches
144  * zero, the object is put on the delayed delete list.
145  * @list_kref: List reference count of this buffer object. This member is
146  * used to avoid destruction while the buffer object is still on a list.
147  * Lru lists may keep one refcount, the delayed delete list, and kref != 0
148  * keeps one refcount. When this refcount reaches zero,
149  * the object is destroyed.
150  * @event_queue: Queue for processes waiting on buffer object status change.
151  * @mem: structure describing current placement.
152  * @persistent_swap_storage: Usually the swap storage is deleted for buffers
153  * pinned in physical memory. If this behaviour is not desired, this member
154  * holds a pointer to a persistent shmem object.
155  * @ttm: TTM structure holding system pages.
156  * @evicted: Whether the object was evicted without user-space knowing.
157  * @cpu_writes: For synchronization. Number of cpu writers.
158  * @lru: List head for the lru list.
159  * @ddestroy: List head for the delayed destroy list.
160  * @swap: List head for swap LRU list.
161  * @val_seq: Sequence of the validation holding the @reserved lock.
162  * Used to avoid starvation when many processes compete to validate the
163  * buffer. This member is protected by the bo_device::lru_lock.
164  * @seq_valid: The value of @val_seq is valid. This value is protected by
165  * the bo_device::lru_lock.
166  * @reserved: Deadlock-free lock used for synchronization state transitions.
167  * @sync_obj: Pointer to a synchronization object.
168  * @priv_flags: Flags describing buffer object internal state.
169  * @vm_rb: Rb node for the vm rb tree.
170  * @vm_node: Address space manager node.
171  * @offset: The current GPU offset, which can have different meanings
172  * depending on the memory type. For SYSTEM type memory, it should be 0.
173  * @cur_placement: Hint of current placement.
174  *
175  * Base class for TTM buffer object, that deals with data placement and CPU
176  * mappings. GPU mappings are really up to the driver, but for simpler GPUs
177  * the driver can usually use the placement offset @offset directly as the
178  * GPU virtual address. For drivers implementing multiple
179  * GPU memory manager contexts, the driver should manage the address space
180  * in these contexts separately and use these objects to get the correct
181  * placement and caching for these GPU maps. This makes it possible to use
182  * these objects for even quite elaborate memory management schemes.
183  * The destroy member, the API visibility of this object makes it possible
184  * to derive driver specific types.
185  */
186 
187 struct ttm_buffer_object {
188 	/**
189 	 * Members constant at init.
190 	 */
191 
192 	struct ttm_bo_global *glob;
193 	struct ttm_bo_device *bdev;
194 	enum ttm_bo_type type;
195 	void (*destroy) (struct ttm_buffer_object *);
196 	unsigned long num_pages;
197 	uint64_t addr_space_offset;
198 	size_t acc_size;
199 
200 	/**
201 	* Members not needing protection.
202 	*/
203 
204 	u_int kref;
205 	u_int list_kref;
206 	/* wait_queue_head_t event_queue; */
207 
208 	/**
209 	 * Members protected by the bo::reserved lock.
210 	 */
211 
212 	struct ttm_mem_reg mem;
213 	struct vm_object *persistent_swap_storage;
214 	struct ttm_tt *ttm;
215 	bool evicted;
216 
217 	/**
218 	 * Members protected by the bo::reserved lock only when written to.
219 	 */
220 
221 	atomic_t cpu_writers;
222 
223 	/**
224 	 * Members protected by the bdev::lru_lock.
225 	 */
226 
227 	struct list_head lru;
228 	struct list_head ddestroy;
229 	struct list_head swap;
230 	struct list_head io_reserve_lru;
231 	uint32_t val_seq;
232 	bool seq_valid;
233 
234 	/**
235 	 * Members protected by the bdev::lru_lock
236 	 * only when written to.
237 	 */
238 
239 	atomic_t reserved;
240 
241 	/**
242 	 * Members protected by struct buffer_object_device::fence_lock
243 	 * In addition, setting sync_obj to anything else
244 	 * than NULL requires bo::reserved to be held. This allows for
245 	 * checking NULL while reserved but not holding the mentioned lock.
246 	 */
247 
248 	void *sync_obj;
249 	unsigned long priv_flags;
250 
251 	/**
252 	 * Members protected by the bdev::vm_lock
253 	 */
254 
255 	RB_ENTRY(ttm_buffer_object) vm_rb;
256 	struct drm_mm_node *vm_node;
257 
258 
259 	/**
260 	 * Special members that are protected by the reserve lock
261 	 * and the bo::lock when written to. Can be read with
262 	 * either of these locks held.
263 	 */
264 
265 	unsigned long offset;
266 	uint32_t cur_placement;
267 
268 	struct sg_table *sg;
269 };
270 
271 /**
272  * struct ttm_bo_kmap_obj
273  *
274  * @virtual: The current kernel virtual address.
275  * @page: The page when kmap'ing a single page.
276  * @bo_kmap_type: Type of bo_kmap.
277  *
278  * Object describing a kernel mapping. Since a TTM bo may be located
279  * in various memory types with various caching policies, the
280  * mapping can either be an ioremap, a vmap, a kmap or part of a
281  * premapped region.
282  */
283 
284 #define TTM_BO_MAP_IOMEM_MASK 0x80
285 struct ttm_bo_kmap_obj {
286 	void *virtual;
287 	struct vm_page *page;
288 	struct sf_buf *sf;
289 	int num_pages;
290 	unsigned long size;
291 	enum {
292 		ttm_bo_map_iomap        = 1 | TTM_BO_MAP_IOMEM_MASK,
293 		ttm_bo_map_vmap         = 2,
294 		ttm_bo_map_kmap         = 3,
295 		ttm_bo_map_premapped    = 4 | TTM_BO_MAP_IOMEM_MASK,
296 	} bo_kmap_type;
297 	struct ttm_buffer_object *bo;
298 };
299 
300 /**
301  * ttm_bo_reference - reference a struct ttm_buffer_object
302  *
303  * @bo: The buffer object.
304  *
305  * Returns a refcounted pointer to a buffer object.
306  */
307 
308 static inline struct ttm_buffer_object *
309 ttm_bo_reference(struct ttm_buffer_object *bo)
310 {
311 	refcount_acquire(&bo->kref);
312 	return bo;
313 }
314 
315 /**
316  * ttm_bo_wait - wait for buffer idle.
317  *
318  * @bo:  The buffer object.
319  * @interruptible:  Use interruptible wait.
320  * @no_wait:  Return immediately if buffer is busy.
321  *
322  * This function must be called with the bo::mutex held, and makes
323  * sure any previous rendering to the buffer is completed.
324  * Note: It might be necessary to block validations before the
325  * wait by reserving the buffer.
326  * Returns -EBUSY if no_wait is true and the buffer is busy.
327  * Returns -ERESTARTSYS if interrupted by a signal.
328  */
329 extern int ttm_bo_wait(struct ttm_buffer_object *bo, bool lazy,
330 		       bool interruptible, bool no_wait);
331 /**
332  * ttm_bo_validate
333  *
334  * @bo: The buffer object.
335  * @placement: Proposed placement for the buffer object.
336  * @interruptible: Sleep interruptible if sleeping.
337  * @no_wait_gpu: Return immediately if the GPU is busy.
338  *
339  * Changes placement and caching policy of the buffer object
340  * according proposed placement.
341  * Returns
342  * -EINVAL on invalid proposed placement.
343  * -ENOMEM on out-of-memory condition.
344  * -EBUSY if no_wait is true and buffer busy.
345  * -ERESTARTSYS if interrupted by a signal.
346  */
347 extern int ttm_bo_validate(struct ttm_buffer_object *bo,
348 				struct ttm_placement *placement,
349 				bool interruptible,
350 				bool no_wait_gpu);
351 
352 /**
353  * ttm_bo_unref
354  *
355  * @bo: The buffer object.
356  *
357  * Unreference and clear a pointer to a buffer object.
358  */
359 extern void ttm_bo_unref(struct ttm_buffer_object **bo);
360 
361 
362 /**
363  * ttm_bo_list_ref_sub
364  *
365  * @bo: The buffer object.
366  * @count: The number of references with which to decrease @bo::list_kref;
367  * @never_free: The refcount should not reach zero with this operation.
368  *
369  * Release @count lru list references to this buffer object.
370  */
371 extern void ttm_bo_list_ref_sub(struct ttm_buffer_object *bo, int count,
372 				bool never_free);
373 
374 /**
375  * ttm_bo_add_to_lru
376  *
377  * @bo: The buffer object.
378  *
379  * Add this bo to the relevant mem type lru and, if it's backed by
380  * system pages (ttms) to the swap list.
381  * This function must be called with struct ttm_bo_global::lru_lock held, and
382  * is typically called immediately prior to unreserving a bo.
383  */
384 extern void ttm_bo_add_to_lru(struct ttm_buffer_object *bo);
385 
386 /**
387  * ttm_bo_del_from_lru
388  *
389  * @bo: The buffer object.
390  *
391  * Remove this bo from all lru lists used to lookup and reserve an object.
392  * This function must be called with struct ttm_bo_global::lru_lock held,
393  * and is usually called just immediately after the bo has been reserved to
394  * avoid recursive reservation from lru lists.
395  */
396 extern int ttm_bo_del_from_lru(struct ttm_buffer_object *bo);
397 
398 
399 /**
400  * ttm_bo_lock_delayed_workqueue
401  *
402  * Prevent the delayed workqueue from running.
403  * Returns
404  * True if the workqueue was queued at the time
405  */
406 extern int ttm_bo_lock_delayed_workqueue(struct ttm_bo_device *bdev);
407 
408 /**
409  * ttm_bo_unlock_delayed_workqueue
410  *
411  * Allows the delayed workqueue to run.
412  */
413 extern void ttm_bo_unlock_delayed_workqueue(struct ttm_bo_device *bdev,
414 					    int resched);
415 
416 /**
417  * ttm_bo_synccpu_write_grab
418  *
419  * @bo: The buffer object:
420  * @no_wait: Return immediately if buffer is busy.
421  *
422  * Synchronizes a buffer object for CPU RW access. This means
423  * command submission that affects the buffer will return -EBUSY
424  * until ttm_bo_synccpu_write_release is called.
425  *
426  * Returns
427  * -EBUSY if the buffer is busy and no_wait is true.
428  * -ERESTARTSYS if interrupted by a signal.
429  */
430 extern int
431 ttm_bo_synccpu_write_grab(struct ttm_buffer_object *bo, bool no_wait);
432 
433 /**
434  * ttm_bo_synccpu_write_release:
435  *
436  * @bo : The buffer object.
437  *
438  * Releases a synccpu lock.
439  */
440 extern void ttm_bo_synccpu_write_release(struct ttm_buffer_object *bo);
441 
442 /**
443  * ttm_bo_acc_size
444  *
445  * @bdev: Pointer to a ttm_bo_device struct.
446  * @bo_size: size of the buffer object in byte.
447  * @struct_size: size of the structure holding buffer object datas
448  *
449  * Returns size to account for a buffer object
450  */
451 size_t ttm_bo_acc_size(struct ttm_bo_device *bdev,
452 		       unsigned long bo_size,
453 		       unsigned struct_size);
454 size_t ttm_bo_dma_acc_size(struct ttm_bo_device *bdev,
455 			   unsigned long bo_size,
456 			   unsigned struct_size);
457 
458 /**
459  * ttm_bo_init
460  *
461  * @bdev: Pointer to a ttm_bo_device struct.
462  * @bo: Pointer to a ttm_buffer_object to be initialized.
463  * @size: Requested size of buffer object.
464  * @type: Requested type of buffer object.
465  * @flags: Initial placement flags.
466  * @page_alignment: Data alignment in pages.
467  * @interruptible: If needing to sleep to wait for GPU resources,
468  * sleep interruptible.
469  * @persistent_swap_storage: Usually the swap storage is deleted for buffers
470  * pinned in physical memory. If this behaviour is not desired, this member
471  * holds a pointer to a persistent shmem object. Typically, this would
472  * point to the shmem object backing a GEM object if TTM is used to back a
473  * GEM user interface.
474  * @acc_size: Accounted size for this object.
475  * @destroy: Destroy function. Use NULL for kfree().
476  *
477  * This function initializes a pre-allocated struct ttm_buffer_object.
478  * As this object may be part of a larger structure, this function,
479  * together with the @destroy function,
480  * enables driver-specific objects derived from a ttm_buffer_object.
481  * On successful return, the object kref and list_kref are set to 1.
482  * If a failure occurs, the function will call the @destroy function, or
483  * kfree() if @destroy is NULL. Thus, after a failure, dereferencing @bo is
484  * illegal and will likely cause memory corruption.
485  *
486  * Returns
487  * -ENOMEM: Out of memory.
488  * -EINVAL: Invalid placement flags.
489  * -ERESTARTSYS: Interrupted by signal while sleeping waiting for resources.
490  */
491 
492 extern int ttm_bo_init(struct ttm_bo_device *bdev,
493 			struct ttm_buffer_object *bo,
494 			unsigned long size,
495 			enum ttm_bo_type type,
496 			struct ttm_placement *placement,
497 			uint32_t page_alignment,
498 			bool interrubtible,
499 			struct vm_object *persistent_swap_storage,
500 			size_t acc_size,
501 			struct sg_table *sg,
502 			void (*destroy) (struct ttm_buffer_object *));
503 
504 /**
505  * ttm_bo_synccpu_object_init
506  *
507  * @bdev: Pointer to a ttm_bo_device struct.
508  * @bo: Pointer to a ttm_buffer_object to be initialized.
509  * @size: Requested size of buffer object.
510  * @type: Requested type of buffer object.
511  * @flags: Initial placement flags.
512  * @page_alignment: Data alignment in pages.
513  * @interruptible: If needing to sleep while waiting for GPU resources,
514  * sleep interruptible.
515  * @persistent_swap_storage: Usually the swap storage is deleted for buffers
516  * pinned in physical memory. If this behaviour is not desired, this member
517  * holds a pointer to a persistent shmem object. Typically, this would
518  * point to the shmem object backing a GEM object if TTM is used to back a
519  * GEM user interface.
520  * @p_bo: On successful completion *p_bo points to the created object.
521  *
522  * This function allocates a ttm_buffer_object, and then calls ttm_bo_init
523  * on that object. The destroy function is set to kfree().
524  * Returns
525  * -ENOMEM: Out of memory.
526  * -EINVAL: Invalid placement flags.
527  * -ERESTARTSYS: Interrupted by signal while waiting for resources.
528  */
529 
530 extern int ttm_bo_create(struct ttm_bo_device *bdev,
531 				unsigned long size,
532 				enum ttm_bo_type type,
533 				struct ttm_placement *placement,
534 				uint32_t page_alignment,
535 				bool interruptible,
536 				struct vm_object *persistent_swap_storage,
537 				struct ttm_buffer_object **p_bo);
538 
539 /**
540  * ttm_bo_check_placement
541  *
542  * @bo:		the buffer object.
543  * @placement:	placements
544  *
545  * Performs minimal validity checking on an intended change of
546  * placement flags.
547  * Returns
548  * -EINVAL: Intended change is invalid or not allowed.
549  */
550 extern int ttm_bo_check_placement(struct ttm_buffer_object *bo,
551 					struct ttm_placement *placement);
552 
553 /**
554  * ttm_bo_init_mm
555  *
556  * @bdev: Pointer to a ttm_bo_device struct.
557  * @mem_type: The memory type.
558  * @p_size: size managed area in pages.
559  *
560  * Initialize a manager for a given memory type.
561  * Note: if part of driver firstopen, it must be protected from a
562  * potentially racing lastclose.
563  * Returns:
564  * -EINVAL: invalid size or memory type.
565  * -ENOMEM: Not enough memory.
566  * May also return driver-specified errors.
567  */
568 
569 extern int ttm_bo_init_mm(struct ttm_bo_device *bdev, unsigned type,
570 				unsigned long p_size);
571 /**
572  * ttm_bo_clean_mm
573  *
574  * @bdev: Pointer to a ttm_bo_device struct.
575  * @mem_type: The memory type.
576  *
577  * Take down a manager for a given memory type after first walking
578  * the LRU list to evict any buffers left alive.
579  *
580  * Normally, this function is part of lastclose() or unload(), and at that
581  * point there shouldn't be any buffers left created by user-space, since
582  * there should've been removed by the file descriptor release() method.
583  * However, before this function is run, make sure to signal all sync objects,
584  * and verify that the delayed delete queue is empty. The driver must also
585  * make sure that there are no NO_EVICT buffers present in this memory type
586  * when the call is made.
587  *
588  * If this function is part of a VT switch, the caller must make sure that
589  * there are no appications currently validating buffers before this
590  * function is called. The caller can do that by first taking the
591  * struct ttm_bo_device::ttm_lock in write mode.
592  *
593  * Returns:
594  * -EINVAL: invalid or uninitialized memory type.
595  * -EBUSY: There are still buffers left in this memory type.
596  */
597 
598 extern int ttm_bo_clean_mm(struct ttm_bo_device *bdev, unsigned mem_type);
599 
600 /**
601  * ttm_bo_evict_mm
602  *
603  * @bdev: Pointer to a ttm_bo_device struct.
604  * @mem_type: The memory type.
605  *
606  * Evicts all buffers on the lru list of the memory type.
607  * This is normally part of a VT switch or an
608  * out-of-memory-space-due-to-fragmentation handler.
609  * The caller must make sure that there are no other processes
610  * currently validating buffers, and can do that by taking the
611  * struct ttm_bo_device::ttm_lock in write mode.
612  *
613  * Returns:
614  * -EINVAL: Invalid or uninitialized memory type.
615  * -ERESTARTSYS: The call was interrupted by a signal while waiting to
616  * evict a buffer.
617  */
618 
619 extern int ttm_bo_evict_mm(struct ttm_bo_device *bdev, unsigned mem_type);
620 
621 /**
622  * ttm_kmap_obj_virtual
623  *
624  * @map: A struct ttm_bo_kmap_obj returned from ttm_bo_kmap.
625  * @is_iomem: Pointer to an integer that on return indicates 1 if the
626  * virtual map is io memory, 0 if normal memory.
627  *
628  * Returns the virtual address of a buffer object area mapped by ttm_bo_kmap.
629  * If *is_iomem is 1 on return, the virtual address points to an io memory area,
630  * that should strictly be accessed by the iowriteXX() and similar functions.
631  */
632 
633 static inline void *ttm_kmap_obj_virtual(struct ttm_bo_kmap_obj *map,
634 					 bool *is_iomem)
635 {
636 	*is_iomem = !!(map->bo_kmap_type & TTM_BO_MAP_IOMEM_MASK);
637 	return map->virtual;
638 }
639 
640 /**
641  * ttm_bo_kmap
642  *
643  * @bo: The buffer object.
644  * @start_page: The first page to map.
645  * @num_pages: Number of pages to map.
646  * @map: pointer to a struct ttm_bo_kmap_obj representing the map.
647  *
648  * Sets up a kernel virtual mapping, using ioremap, vmap or kmap to the
649  * data in the buffer object. The ttm_kmap_obj_virtual function can then be
650  * used to obtain a virtual address to the data.
651  *
652  * Returns
653  * -ENOMEM: Out of memory.
654  * -EINVAL: Invalid range.
655  */
656 
657 extern int ttm_bo_kmap(struct ttm_buffer_object *bo, unsigned long start_page,
658 		       unsigned long num_pages, struct ttm_bo_kmap_obj *map);
659 
660 /**
661  * ttm_bo_kunmap
662  *
663  * @map: Object describing the map to unmap.
664  *
665  * Unmaps a kernel map set up by ttm_bo_kmap.
666  */
667 
668 extern void ttm_bo_kunmap(struct ttm_bo_kmap_obj *map);
669 
670 /**
671  * ttm_fbdev_mmap - mmap fbdev memory backed by a ttm buffer object.
672  *
673  * @vma:       vma as input from the fbdev mmap method.
674  * @bo:        The bo backing the address space. The address space will
675  * have the same size as the bo, and start at offset 0.
676  *
677  * This function is intended to be called by the fbdev mmap method
678  * if the fbdev address space is to be backed by a bo.
679  */
680 
681 /* XXXKIB
682 extern int ttm_fbdev_mmap(struct vm_area_struct *vma,
683 			  struct ttm_buffer_object *bo);
684 */
685 /**
686  * ttm_bo_mmap - mmap out of the ttm device address space.
687  *
688  * @filp:      filp as input from the mmap method.
689  * @vma:       vma as input from the mmap method.
690  * @bdev:      Pointer to the ttm_bo_device with the address space manager.
691  *
692  * This function is intended to be called by the device mmap method.
693  * if the device address space is to be backed by the bo manager.
694  */
695 /* XXXKIB
696 extern int ttm_bo_mmap(struct file *filp, struct vm_area_struct *vma,
697 		       struct ttm_bo_device *bdev);
698 */
699 /**
700  * ttm_bo_io
701  *
702  * @bdev:      Pointer to the struct ttm_bo_device.
703  * @filp:      Pointer to the struct file attempting to read / write.
704  * @wbuf:      User-space pointer to address of buffer to write. NULL on read.
705  * @rbuf:      User-space pointer to address of buffer to read into.
706  * Null on write.
707  * @count:     Number of bytes to read / write.
708  * @f_pos:     Pointer to current file position.
709  * @write:     1 for read, 0 for write.
710  *
711  * This function implements read / write into ttm buffer objects, and is
712  * intended to
713  * be called from the fops::read and fops::write method.
714  * Returns:
715  * See man (2) write, man(2) read. In particular,
716  * the function may return -ERESTARTSYS if
717  * interrupted by a signal.
718  */
719 
720 extern ssize_t ttm_bo_io(struct ttm_bo_device *bdev, struct file *filp,
721 			 const char *wbuf, char *rbuf,
722 			 size_t count, off_t *f_pos, bool write);
723 
724 extern void ttm_bo_swapout_all(struct ttm_bo_device *bdev);
725 
726 /**
727  * ttm_bo_is_reserved - return an indication if a ttm buffer object is reserved
728  *
729  * @bo:     The buffer object to check.
730  *
731  * This function returns an indication if a bo is reserved or not, and should
732  * only be used to print an error when it is not from incorrect api usage, since
733  * there's no guarantee that it is the caller that is holding the reservation.
734  */
735 static inline bool ttm_bo_is_reserved(struct ttm_buffer_object *bo)
736 {
737 	return atomic_read(&bo->reserved);
738 }
739 
740 #endif
741